It is becoming quite common for vehicles to have both a driver's air bag placed within the steering wheel and a front passenger's air bag provided in the instrument panel. In the manufacture of such instrument panels, a separate door or closure is normally provided within the rigid insert which forms a portion of the instrument panel. The door serves to conceal an air bag assembly, and it has been common practice to connect the door to the insert by using separate fastener means and provide a weakened section within the door or along one side of the door so as to allow the door to tear loose from its support and pivot to an open position as a result of the inflating air bag. Although arrangements of this sort for connecting the door to the main portion of the insert permit the door to open and function properly, it should be apparent that the use of separate fasteners for joining the door to the insert increases the cost of manufacturing and assembling the panel. In addition, by making the door as a separate part, a problem of fit and finish is inherently created.
One example of an instrument panel of the type in which a door is connected to the substrate of the panel through separate fastener means can be seen in U.S. Pat. No. 5,082,310 issued to David J. Bauer on Jan. 21, 1992. Several door arrangements are shown in the Bauer patent that have multiple sections and, in each case, the instrument panel substrate is joined the a door section by separate fastener means. Although the Bauer patent does indicate that the door sections could be made integral with the instrument panel substrate, there is no teaching or disclosure of the method or means for accomplishing this result, which, if done properly, could solve the problem mentioned above. In addition, the U.S. Pat. No. 4,335,068 to Hemery, issued on Jun. 15, 1982, does show the use of two different plastic materials for molding an article. The Hemery patent, however, relates to containers and not to closures or doors for air bag assemblies nor does this patent teach mechanical interlocking of two different plastic materials as would be required for providing an acceptable hinged connection for a door of this type.